Trichodinids (Ciliophora: Peritrichida) parasitic on gills of freshwater fishes, Carassius auratus and Aristichthys nobilis from China, with the description of Trichodina subtilihamata sp. nov. Author Tang, Fahui Author Zhao, Yuanjun zhao-yuanjun@hotmail.com Author Tao, Yanfei text Zootaxa 2007 2007-09-12 1582 1 39 48 https://biotaxa.org/Zootaxa/article/view/zootaxa.1582.1.4 journal article 10.11646/zootaxa.1582.1.4 1175­5334 5097603 3EF83504-21B0-47BA-9484-49C27A5DBDE0 Trichodina mutabilis Kazubski & Migala, 1968 ( Figs. 2C–D , 3G–H ) Host: Carassius auratus and Aristichthys nobilis . Location: Gills. Prevalence: Out of 15 Carassius auratus examined, one was infected (6.7 %); and out of 24 Aristichthys nobilis examined, one was infected (4.2 %). FIGURE 2. Photomicrographs of silver impregnated adhesive discs of Trichodina spp. A –B. Trichodina kazubski Van As & Basson, 1989 ; C–D: Trichodina mutabilis Kazubski & Migala, 1968 . Scale bar = 20m. Locality: Chongqing , China ( 29º5' N , 106º5' E ) . Date of sampling: March, 2004 and April, 2005. Description. Population from Carassius auratus . Medium to large-size with disc-shaped body and cell diameter 56.0 – 74.0µm (62.9 ± 5.6). Diameter of adhesive disc 48.0 – 62.0µm (54.8 ± 3.3). Border membrane 4.0 – 6.0µm (5.1 ± 0.3) in width. Diameter of denticulated ring 35.0 – 42.0µm (38.2 ± 2.3). Number of denticles about 26 – 28 (n = 12). Number of radial pins per denticle 8 – 11 (n = 12). Span of denticle 14.0 – 20.0µm (16.8 ± 2.9). Length of denticle 6.0 – 8.0µm (6.8 ± 1.3). Blade shape broad and oblong, 6.0 – 7.0µm (6.3 ± 0.3) in length. Width of central part 2.0 – 3.0µm (2.6 ± 0.3). Length of ray 6.0 – 10.0µm (8.2 ± 1.7). Nuclear stains not available and therefore no biometric data of nuclear apparatus presented. Adoral ciliary spiral turns about 380º – 400º around peristomial disc. Population from Aristichthys nobilis FIGURE 3. Diagrammatic drawing of the denticles of Trichodina spp. A –B. Trichodina subtilihamata sp. nov. ; C: Trichodina uniforma Van As & Basson, 1989 ; D: Trichodina nigra Lom, 1960 ; E–F: Trichodina kazubski Van As & Basson, 1989 ; G–H: Trichodina mutabilis Kazubski & Migala, 1968 . Cell diameter 57.0 – 65.0µm (61.2 ± 3.3). Diameter of adhesive disc 47.0 – 55.0µm (50.4 ± 3.2). Border membrane 5.0 – 6.0µm (5.8 ± 0.4) in width. Diameter of denticulated ring 29.0 – 34.0µm (31.4 ± 2.1). Number of denticles about 23 – 30 (n = 12). Number of radial pins per denticle 9 – 11 (n = 12). Span of denticle 15.0 – 16.0µm (15.8 ± 0.5). Length of denticle 7.0 – 8.5µm (7.9 ± 0.5). Blade shape broad and oblong, 6.0 – 6.5µm (6.1 ± 0.1) in length. Width of central part 3.5 – 4.5µm (4.0 ± 0.3). Length of ray 7.0 – 7.5µm (7.1 ± 0.2). No availble nuclear apparatus observed. Adoral ciliary spiral turns about 380º – 400º around peristomial disc. Description of denticle ( Figs. 3G–H ): Blade broad and rectangle; anterior blade surface and posterior surface smooth and straight, and anterior blade surface touching or almost extending past Y+1 axis; distal blade surface straight and almost at the same level as tangent point. Central part relatively developed with rounded point fitting tightly into preceding denticle. Ray connection short but stumpy, inconspicuous and barely distinguishable from ray. Ray relatively developed, straight and directed in anterior. Ray apophysis not prominent and ratio between denticle above and denticle below X axis less than one. Remarks. Trichodina mutabilis has been described from different hosts from various localities mostly in Europe, West Africa and Australia , and mainly from cyprinids and in the majority of cases from the genus Carassius . It was originally described from carps by Kazubski & Migala (1968) and evidently exhibited great variability in morphology. Infestations have been reported from a variety of fish hosts such as Carassius auratus , Cyprinus carpio , Leucapsius delineatus and Rhodeus sericeus ( Lom, 1970b ; Basson, et al., 1983; Van As & Basson, 1989 ; Dove & O’Donoghue, 2005 ). All these descriptions, however, vary in the denticle morphology, suggesting that perhaps these descriptions represent an assemblage of similar species. Two populations of T . mutabilis from Carassius auratus and Aristichthys nobilis were investigated in the present study, and Aristichthys nobilis is a new host record for T . mutabilis . The specimens from the two hosts show very small range of variability in the denticle morphology. In the population from Carassius auratus ( Figs.3G ), blade connection is broad and the tip of central part is not extending than half way to Y-1 axis; whereas in population from Aristichthys nobilis ( Figs.3H ), blade connection is delicate and tip of central part is extending more than half way to Y-1 axis even touches Y-1 axis. T . mutabilis is a well known and widely distributed gill parasite from mainly carp in Europe. In southern Africa, it was only found on the host, Carassius auratus ( Van As & Basson, 1989 ) . Later, fins and gills of Cyprinus carpio in Australian were found to be parasitized by this species ( Dove & O’Donoghue, 2005 ). Up to now, it has not been reported in Asia, so as a new area distribution, Chongqing China established the first record.